As a technique for recognizing an image of a predetermined recognition target land object included in image information obtained on a road, Patent Document 1 identified below discloses the following technique relating to a stop line recognizing apparatus. This stop line recognizing apparatus includes area brightness detecting means for detecting brightness of a set area which locates ahead or forwardly on a traveling road and extends longitudinally along the width of the traveling vehicle, time-series brightness change comparing means for comparing time-series change in brightness in the set area and a stop line determining means for determining presence/absence of a stop line based on the time-series brightness change detected in the set area. More particularly, a plurality of set areas are provided continuously along the vehicle width direction at a lower region in an original image inputted from a CCD camera. Then, if a mean brightness of any one of the plural set areas changes from low to high and then low again, the apparatus determines that a stop line exists.
The Patent Document 1 above further discloses a technique relating to a vehicle drive assisting system including, in addition to the stop line recognizing apparatus described above, three-dimensional object recognizing means for recognizing a three-dimensional object present forwardly on the traveling road, and alarm controlling means for issuing an alarm if the stop line recognizing apparatus has recognized a stop line and a three-dimensional object has been recognized immediately forwardly of (ahead of) that stop line. According to this vehicle drive assisting system, a pair of right and left stereo images obtained by a CCD camera having a stereoscopic optical system are processed to calculate three-dimensional distance distribution information over the entire images. Then, based on this distance distribution information, the system detects at a high speed three-dimension position data of e.g. a road geometry, a plurality of three-dimensional objects, etc. That is, by utilizing three-dimensional position information derived from the distance image, data relating to a white line present on the actual road is separated/extracted. On the other hand, parameters of a road model stored in advance in the system are changed or modified to suit the actual road geometry, thus recognizing the road geometry. Further, based on the detected road geometry, the system picks out data relating to an area upwardly of the road surface and eliminates noise contained in the distance image, thus extracting data of a three-dimensional object such as another vehicle traveling ahead, from the distance image. Moreover, the system divides the distance image by a predetermined interval into a grid of segments and makes a histogram for each grid segment, thus calculating the distance to the three-dimensional object. Then, based on distance data of the three-dimensional object for each segment, the contour image of the object is extracted and based on the dimensions of its shape and its position, the system recognizes e.g. the kind of the object.
[Patent Document 1]
Japanese Patent Application “Kokai” No. 2003-85562 (pages 2-4, FIGS. 1-3)